Combined pulp cleaning system including high and low pressure drop hydrocyclone cleaners

ABSTRACT

A method and apparatus for effecting low-pressure separation from a suspension of reclaimed wastepaper of both cellulose pulp fibers and light impurity particles having a specific gravity less than that of the pulp fibers, characterized by the use of a wastepaper cleaner operable in the low-pressure hydrocyclone mode to deposit the heavier pulp fibers at the bottom of a chamber and to establish an upward flow of the lighter particles in a vertical vortex in the central portion of the chamber. The invention also includes a method and apparatus for separating the cellulose pulp fibers from a reclaimed wastepaper suspension by a combined high-pressure drop low-pressure drop separation process, use being made of a high-pressure drop hydrocyclone separator that is connected in unitized construction with the low-pressure wastepaper cleaner. Finally, an improved waste-paper cleaning system is disclosed including in combination with the highpressure drop low-pressure drop separator a further low-pressure wastepaper cleaner for effecting second-stage cleaning of the lighter separated impurity particles, and a further hydrocyclone separator for effecting second-stage cleaning of the heavier separated impurity particles.

United States Patent 1191 1111 3,928,186

Zemanek Dec. 23, 1975 COMBINED PULP CLEANING SYSTEM INCLUDING I-IIGH ANDLOW PRESSURE Primary Examiner-Frank W. Lutter DROP HYDROCYCLONE CLEANERSAssistant ExaminerRalph J. Hill [75] Inventor: Rudolf Zemanek,Vancouver, Wash. Attorney Agent or Firm-Lawrence Laubscher [73]Assignee: Boise Cascade Corporation, Boise, [57] ABSTRACT Idaho A methodand apparatus for effecting low-pressure [22] Filed: July 24, 1973separation from a suspension of reclaimed wastepaper of both cellulosepulp fibers and light impurity parti- 1 PP 332,068 cles hav ng aspecific gravity less than that of the pulp 1 1 fibers, characterized bythe use of a ,wastepaper 52 11.5. C1. 209/211 919999 P9table theWV-Pressure hydmcychne 51 Int. (:1. 1304c 5/103 mode 9 the heavier Pfibers at the b99919 5 Fidd f s 209011. 210/512 R 512 M of a chamber andto establish an upward flow of the 210/84; lighter particles in avertical vortex in the central portion of the chamber. The inventionalso includes a [56] References Cited method and apparatus forseparating the cellulose UNITED STATES PATENTS pulp fibers from areclaimed wastepaper suspenslon by a comb1nedh1gh-pressure droplowpressure drop sep- 2,377,524 6/1945 I Samson et all. 209/211 arations u b i ad f a high-pressure 3:333:33; 3/132? 52213111111111?" 11111151132 35,; 9 11999191109989.9999 that is inimit- 2.s43,26s 7/1958Rakowsky ..209/211x constructo the bwpressure wastepaper cleaner.Finally, ,an improved waste-paper cleaning 209/211 X 210/84 X system 1sd1sclosed including 1n combmation with the 209/211 X high-pressure droplow-pressure drop separator a fur- 209/168 X ther low-pressurewastepaper cleaner for effecting se- 209/211 cond-stage cleaning of thelighter separated impurity u 209/211 particle's, and afurtherhydrocyclone separator for ef- 210/512 R fecting second-stage cleaningof the heavier separated 2,849,930 9/1958 Freeman et al. 3,052,3619/1962 Whatley et a1 3,425,545 2/ 1969 Zemanek et al.. 3,428,175 2/ 1969l-lukk i 3,486,619 12/1969 Grundelius et al. 3,543,932 12/1970 Rastatter3,696,934 10/1972 Oisi 3.747.757 7/1973 Kalthoffetal.... 209/211 i ufi 1.385 9/1973 Pouillon 209/168 x mp ty Pa 3,764,005 1011973 Zemanek 209211 9 Claims, 5 Drawing Figures Light Porticti Impurity Rejects PulpFiber Accepts US. Patent Dec.23,1975 Sheet1of3 3,928,186

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US. Patent Dec. 23, 1975 Sheet 3 of 3 3,928,186

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commcwawsw $303525 35 mm (among others), hydrocyclone apparatus forseparating particles of different specific gravities from. a paperpulpsuspension are'well known in the art. More particularly, theseknownhydrocyclone separators are suitable for separating-from asuspension impurity particles having a specifiogravity that is greaterthan that of the cellulosepulp. In order to remove particles ofimpurities having a specific gravity less than that of the cellulosepulp fibers,-it has been proposed to use separating screens which areefficient inremoving only the large and spherical-plastic particles,since the smaller and flat particles pass readily through the screenopenings (holesor slots);. .The conventional hydrocyclone is incapableof removingsynthetic plastic material, or materials suchzasink, hot meltor thelike. j

i The present, invention is based on the concept of removing:the-lighter particles from the wastepaper suspension by a lowpressureprocess.

Accordingly, the primary object of the present invention is toprovide alow-pressure wastepapercleaner method and apparatus for separating froma reclaimed wastepaper suspension both the cellulose .pulp fibers andthe lighterimpurity particles having a specific gravity less than thatof the pulp fibers.The suspension is introduced at relatively lowpressure (on the order of 5 psig) tangentially intothe upper end of alow-pressure drop hydrocyclone chamber having an outlet at its lower endthrough which are discharged the heavier pulp fibers that are throwncentrifugally outwardly and travel downwardly in the chamber in ahelical path. The lighter impurity particles are displaced radiallyinwardly .in the chamber and engage an upwardly convergent" conicaldiverter that establishes an upward vortex flow centrally within thechamber, whereby the lighter impurity particles may be dispensed via anoutletvthat communicates with the upper end of the chamber. i

A further objectof the present invention is to provide a high-pressuredrop low-pressure drop method and apparatus for separating in threefractions from a reclaimed wastepaper suspension the cellulose, pulpfibers, heavy impurity particles having a specific gravity greater thanthat of the pulp fibers, and light impurity particles'l aying a specificgravity lower than that of the pulp fibers. To this end, a high-pressuredrop hydrocyclone iscij eeted colinearly in spaced relation below theaforementioned low-pressure drop wastepaper cleaner, an "intermediatehousing being rigidly connected, between the high-pressure hydrocyclonecleaner and the'low-pressure dropwastepaper cleaner 10 define .a nitaryrigid separator having separate outlets for' fdis'cliarging thecellulose pulp fibers, the light impurity particles and the heavyimpurity particles, 'res'pecti'v'elyff Another'objec tof the presentinvention is to provide an improved system for'acc'urately separatingthe pulp fibers and the light and heavy impurity particles from areclaimed wastepaper cleaner suspension, character- 'ized inthat-the'light particle outlet of the high-pressure drop low-pressuredropseparator is connected with a second-stage low-pressure wastepapercleaner which supplies at its upper outlet the final light particlerejects and returns from its lower outlet to the originalsuspensionvtank the suspension which includes reclaimable cellulose pulpfibers. Furthermore, the heavy rejects discharged from the lower outletof the high-pressure drop low-pressure drop separator may be fed to theinlet of a further hydrocyclone separator (such as the two-bodyseparator of theaforementioned Zemanek application Serial No. 117,566)for separation into the final heavy particle rejects and a suspensioncontaining the cellulose pulp fibers that is returned to the originalsuspension supply tank and/or the heavy particle reject tank associatedwith the-high-pressure drop low-pressure drop cleaner.

Other objects and advantages of the invention will become apparent froma study of the following specification when viewed in the light of theaccompanying drawing, in which: 7

FIG. 1 is a diagrammatic sectional elevational view of a cylindricalembodiment of the low-pressure drop wastepaper cleaner of the presentinvention;

FIG. 2 is a diagrammatic sectional elevational view of a modification ofthe wastepaper cleaner of FIG. 1 wherein the lowerportion of the housingis conical;

FIG. 3 is a diagrammatic sectional elevational view of ahigh-pressure'drop low-pressure drop separator apparatus thatincorporates the operating principles of the wastepaper cleaner of FIG.1;

FIG. 4 is a detailed view of a modification of the apparatus of FIG..3;and

FIG. 5 is an improved wastepaper cleaning system that includes thewastepaper cleaner of FIG. 1 and the high-pressure drop low-pressuredrop separator apparatus of FIG. 3.

Referring first more particularly to FIG. 1, the wastepaper cleaner isoperable to separate from the cellulose pulp fibers of a wastepaper pulpsuspension the lighter impurity particles of materials such as syntheticplastics, ink, adhesives, hot melt particles and the like. Use is madeof a cylindrical housing 2 containing a low pressure drop-chamber 4, aninlet 6 for introducing the suspension tangentially into the upper endof the chamber, and first and second outlets 8 and 10 arranged centrallyin the bottom and top walls of the chamber, respectively. Mounted withinthe bottom opening 8 is a diverter means 12 including a tubular bottomportion 12a upon the upper portion of which is supported a conicalupwardly convergent portion 12b. As illustrated in the drawing, theconical portion is supported by the tubular bottom portion at anelevation greater than that of the outlet opening. The cylindricalportion contains a tangential discharge slot 12c for the discharge ofmaterial from the chamber 4 into the diverter chamber 12d, and dischargeconduit 14 communicates with the lower'end of the diverter chamber.Throttle valve 16connected in the conduit 14 affords means forregulating the back pressure in chambers 12d and 4. Mounted in thesecond outlet l0v is a baffle 18 the lower end of which extends to alevel below that of the inlet 6, thereby to partially isolate the secondoutlet -10 from the inlet 6.

' In" operation, the wastepaper suspension is supplied-at a relativelylow pressure (on the order of 5 psig) and a relatively low flowratetangentially into the upper end of the chamber 4 via inlet 6. As thesuspension flows downwardly in the chamber 4 toward the outlet 8, theheavier cellulose pulp fibers are thrown centrifugally outwardly andtravel downwardly in a helical path adjacent the chamber side wall,whereupon at the bottom of the chamber the pulp fiber-liquid carriersuspension flows through the discharge slot 120, and helicallydownwardly in the diverter chamber 12d and the discharge conduit 14.Owing to the centrifugal helical flow of the heavier cellulose pulpfibers the lighter impurity particles are displaced inwardly of thechamber 4 and engage the conical diverter surface 12b, whereupon anupwardly directed low-pressure vortex flow of the lighter impurityparticles is established in the central portion of the chamber andoutwardly therefrom via the second outlet 10.

It has been found in practice that owing to the lowpressure upwardmovement of particles within the central portion of the housing, thereare removed by the low pressure central vortex not only the lighterimpurity particles but also relatively fine particles of higher specificgravity which are not separated by centrifugal force. Preferably theoutlet pressure of discharge conduit 16 is atmosphere, whereby arelatively low-pressure drop of about psig is achieved.

In the modification of FIG. 2, the housing 2' includes a cylindricalupper portion 2a and a conical downwardly convergent lower portion 2b,thereby to effect a slightly greater acceleration of the heavier pulpfibers adjacent the bottom portion of the chamber. The structure andoperation of this embodiment is otherwise similar to that of FIG. 1,like parts being identified by primed reference numerals.

Referring now to the high-pressure drop low-pressure drop embodiment ofFIG. 3, a reclaimed wastepaper suspension containing cellulose pulpfibers and heavy and light impurity particles having specific gravitiesgreater and less than that of therpulp fibers, respectively, is suppliedat a relatively high pressure (on the order of -50 psig) to ahigh-pressure drop downwardly convergent conical hydrocyclone chamber 24contained within the lower portion 22a of the housing 22. The suspensionis introduced tangentially into the hydrocyclone chamber via inlet 26,whereupon the suspension flows downwardly in the chamber toward thefirst outlet 28. Owing to centrifugal force, the heavier impurityparticles assume a downward helical path adjacent the wall surface ofthe chamber 24 and are discharged via the first outlet 28. The cellulosepulp fibers and the lighter impurity particles are displaced radiallyupwardly in the chamber 24 and assume an upward vortex flow fordischarge via baffle 29 and a second discharge opening 20 contained inthe upper end wall of chamber 24. The discharge pressure isapproximately 5 psig, whereupon the pressure drop between the inlet andoutlets of the hydrocyclone separator is about 25 to 45 psig for inletpressures of 30 to 50 psig, respectively.

The low-pressure suspension of cellulose pulp fibers and lighterimpurity particles is introduced into a cylindrical intermediate chamber34 contained in an intermediate portion 22b of the housing, the sidewall portion of said intermediate chamber containing an outlet 36 whichcommunicates via conduit 38 with the inlet 106 of the low-pressurechamber 104 contained in the upper portion 220 of the housing 22. Theupper housing portion 220 contains a first outlet 108 that communicateswith the bottom portion of the chamber 104, and a second outlet 110centrally arranged in the upper wall of the chamber. Arranged in thebottom of the chamber are diverter means 112 including a cylindricallower portion 112a and an upwardly convergent conical portion 112b.Discharge conduit 114 containing throttle valve 116 communicates withthe first outlet 108, and arranged in the second outlet is the bafflemeans 118 having a tubular lower portion 118a that extends downwardly inthe chamber 104 at least to the level of the inlet 106, thereby toisolate the second outlet from the inlet.

As the suspension introduced via inlet 106 flows downwardly in chamber104 toward the outlet 108, the heavier cellulose pulp fibers are throwncentrifugally outwardly toward the wall of the chamber and passdownwardly in a helical path for discharge via outlet 108. The lighterimpurity particles are displaced inwardly and engage the conicaldiverter portion 112b, whereupon a vortex flow of the lighter impurityparticles is established upwardly in the central portion of the chamber104 toward the outlet 110 for discharge via the opening 120 contained inthe upper end wall 118b of the baffle means.

Consequently, it is apparent that the high-pressure drop low-pressuredrop apparatus of FIG. 3 is operable by a single unitary construction toseparate from the initial reclaimed wastepaper suspension heavy impurityparticles at outlet 28, light impurity particles at outlet 120, andacceptable cellulose pulp fibers at outlet 1 14. The back pressure ofchamber 104 (and, to a certain extent, the back pressures of chambers 34and 24) may be controlled by appropriate adjustment of throttle valve116.

As shown in the modification of FIG. 4, in the event that the suspensioncontains a certain degree of air, the second outlet 120' is arranged inthe side wall of the baffle and an air outlet 122 is provided in theupper end wall 118b of the baffle. Consequently, air is readilyseparated from the suspension adjacent the light particle outlet.

The wastepaper cleaner and high-pressure drop lowpressure dropcomponents are particularly suitable for use in the improved wastepapercleaning system illustrated in FIG. 5. The reclaimed wastepapersuspension-which has a 0.30.7% concentration and includes cellulose pulpfibers, heavy impurity particles having a specific gravity higher thanthat of the pulp fibers, and light impurity particles having a specificgravity lower than that of the pulp fibers--is introduced in the supplytank and is pumped by pump 152 at a relatively high pressure (30-50psig) to the inlet 226 of the high-pressure drop chamber 224 containedin the lower portion 222a of the housing 222 of the highpressure droplow-pressure drop separator 222. The heavy impurity particles aredeposited into tank 154 via outlet 228 and are pumped by pump 156 to theinlet 158 of the two-body separator apparatus 160 (which apparatus isdisclosed in detail in the Zemanek application Ser. No. 117,566). Theseparator 160 serves as a second-stage device including a first outlet162 for supplying the final heavy impurity particles, a second outlet164 for returning to the supply tank 150 a first suspension of a lighterportion of the heavy impurity particles (which possibly includesredeemable cellulose pulp fibers), and a third outlet 166 which returnsto the heavy reject tank 154 a second suspension of a heavier portion ofthe heavy impurity particles (which possibly includes a small quantityof redeemable pulp fibers) third .outlet 166 to the heavy particlereject tank 154.

The low-pressure upper wastepaper cleaner portion 2220 of the combinedhigh-pressure drop low-pressure drop separator 222 serves to provide theacceptable cellulose pulp fibers via first outlet 308 and dischargeconduit 314, and the light impurity particle rejects are supplied totank 170 via the second outlet 320. These rejects are pumped by pump 172at a relatively low pressure (about 5 psig) to the inlet 406 of thelow-pressure drop wastepaper cleaner 402, which apparatus serves as asecond stage separator for the light impurity particles. Final lightparticle rejects are supplied via watepaper cleaner outlet 410, and thesuspension produced at outlet 408 (which may include some acceptablecellulose pulp fibers) is returned to the supply tank 150.

While the improved system of FIG. 5 has been disclosed with regard tothe separation of impurities from reclaimed wastepaper stock, it isapparent that the system has utility in many other applications, such asthe cleaning of virgin pulp or paper stock ahead of a paper machine. 1

Although in accordance with the PatentStatutes the preferred form andembodiments of the invention has been disclosed, it will be apparentthat various modifications may be made without deviating from myinventive concept.

What is claimed is:

l. The method of separating from a reclaimed wastepaper suspension thecellulose pulp fibers and heavy and light particles of impurities havingspecific gravities greater and less, respectively, than that of the pulpfibers, which comprises the steps of I a. supplying the suspensiontangentially at a pressure of about 30-50 psig. into the upper end of ahighpressure centrifugal hydrocyclone separator chamber;

b. withdrawing the heavy impurity particle rejects from the bottom ofthe high-pressure chamber, whereby a vertical vortex of light impurityparticles and pulp fibers is formed in the center of the highpressurechamber;

0. withdrawing from the upper end of the high-pressure chamber thesecond suspension including the pulp fibers and the light impurityparticles;

d. supplying the second suspension at a pressure of about 5 psig.tangentially into the upper end of a low-pressure hydrocyclone chamber;

e. withdrawing from the bottom of the low-pressure chamber a thirdsuspension including the pulp fibers that flow helically downwardlyadjacent the wall of the low-pressure chamber, whereby the lightparticles are displaced radially inwardly and downwardly in thelow-pressure chamber;

f. diverting the light particles upwardly to form a vortex flow thereofin the central portion of the low-pressure chamber; and

g. withdrawing from the top of the low-pressure chamber a fourthsuspension including the light impurity particles.

2. The method as defined in claim 1, and further including the steps ofh. supplying the fourth suspension tangentially at a pressure of about 5psig. to the upper end of a second low-pressure chamber;

i. withdrawing from the bottom of the second lowpressure chamber thesuspension including reclaimable pulp fibers and returning thissuspension to the original suspension; and

j. withdrawing from the upper end of the second low-pressure chamber thefinal light impurity particles.

3. The method as recited in claim 2, and further including the'steps ofk. feeding a suspension including the heavy impurity particlesdischarged from the high-pressure centrifugal hydrocyclone chamber tothe upper end of a second high-pressure centrifugal hydrocyclonechamber;

1. withdrawing final heavy impurity particles from the lower end of thesecond hydrocyclone chamber; and

m. returning to the suspension source of at least one of hehigh-pressure hydrocyclone chambers from the upper end of the secondhigh-pressure hydrocyclone chamber the suspension which includesreclaimable cellulose pulp fibers.

4. Low-pressure drop apparatus for separating from a liquid suspensioncellulose pulp fibers and particles of impurities having a specificgravity less than that of the cellulose pulp fibers, comprising a. meansfor supplying said suspension under pressure;

b. a housing having top, bottom and side walls defining a verticalhydrocyclone chamber, said housing being cylindrical and having auniform diameter throughout its length,

l. the upper portion of said housing side wall containing an inletopening connected with said suspension supply means for supplying saidsuspension tangentially into the upper end of said chamber;

2. the lower end of said housing containing a first outlet opening;

3. the central portion of the upper end of said housing containing asecond outlet opening;

. upwardly convergent conical diverter means centrally mounted on thebottom wall of said vertical hydrocyclone chamber, said diverter meansincluding an upwardly convergent conical diverter member, andcylindrical support means supporting said conical diverter member agiven distance above said housing bottom wall and above said firstoutlet opening, said cylindrical support means having an outer diameterwhich correponds with the maximum diameter of said conical divertermember; and

d. tubular baffle means connected with the central portion of thehousing top wall and communicating at its upper end with the secondoutlet opening, the lower end of said baffle means extending downwardlyin said chamber to a level slightly below that of said inlet opening;

e. the pressure of said suspension supply means being such as toestablish a pressure difference of about 5 psig. between said inletopening and said firstoutlet opening, whereby the pulp fibers areseparated from the suspension by centrifugal force and pass downwardlyin the chamber in an outer helical path adjacent the side wall surfaceof the chamber for discharge via said first outlet, said diverter meansestablishing in the central portion of the chamber within the outerhelical path an upwardly directed small helical vortex flow of theimpurity particles of the suspension for discharge via said secondoutlet opening.

5. Combined high-pressure-drop low-presure-drop apparatus for separatingfrom a liquid suspension cellulose pulp fibers, and first and secondgroups of impurities having specific gravities greater than and lessthan that of said pulp fibers, respectively, comprising a. means forsupplying said suspension under pressure; 7

b. a unitary housing including a lower portion containing a verticallyarranged downwardly convergent conical high-pressure-drop hydrocycloneseparation chamber, an upper portion containing a vertically arrangedgenerally cylindrical low-pressure-drop separation chamber, and a middleportion containing an intermediate chamber,

1. the upper side wall portion of said lower chamber containing a firstinlet connected with said suspension supply means for supplying saidsuspension tangentially into said lower chamber;

2. the lower end of said lower chamber containing a first outlet;

3. the central portion of the upper end of said lower chamber containinga second outlet;

4. the central lower portion of said intermediate chamber containing asecond inlet communicating with said second outlet;

5. the side wall portion of said intermediate chamber containing a thirdoutlet;

6. the upper side wall portion of said upper chamber containing a thirdinlet connected with said third outlet for introducing the suspensiontangentially into the upper end of said upper chamber;

7. the lower side wall portion of said upper chamber containing a fourthoutlet; and 8. the top wall portion of said upper chamber containing afifth outlet; and c. upwardly convergent conical diverter meanscentrally mounted on the bottom wall of said chamber, said divertermeans including an upwardly convergent conical diverter member, andmeans supporting saiddiverter member a given distance above,

said housing bottom wall, whereby in said lower chamber the first groupof impurities is separated from said suspension by centrifugal force fordischarge via said first outlet, the remaining pulp fiber particles andsecond group of impurities having an upwardly directed vortex flowwithin said lower chamber fortangential introduction into said upperchamber via said second outlet, said second inlet, said intermediatechamber, said thirdo'utlet and said third inlet, whereby the pulpfibersa'res'eparated -by centrifugal force from said suspension in said upperchamber for discharge .via said fourth outlet, and said diverter meanscause said second group of particles to form an upwardly directed vortexin the central portion of saidupper chamber for dischargevia said fifthoutlet. 6. Apparatus as defined in claim 5, wherein said fourth outletis connected with atmosphere and said suspension supply means has apressure of about 30 to 50 psig, said lower chamber having a dischargepressure at said second outlet of about psig.

7. Apparatus as defined in claim 5, and further including second-stageheavy particle hydrocyclone separator means for recleaning the heavyimpurity particles discharged from first outlet, said second-stageseparator means being of the two-body type including a conical housingwhich is divided into upper and lower chambers by a horizontal baffle,said separator means including a fourth inlet for introducing the heavyparticles from said first outlet tangentially into the upper end of theupper chamber of said second-stage separator, a sixth outlet (162) fordischarging the final heavy rejects from the lower end of the lowerchamber of said second-stage separator, a seventh outlet (166) forreturning to the heavy particle rejects discharged from the first outletthe lighter impurity particles that are displaced upwardly in thecentral portion of said lower chamber, and an eighth outlet (164) forreturning to the first inlet the lighter particles that are directedupwardly in the central portion of said upper chamber.

8. Apparatus as defined in claim 5, and further including light particlesecond-stage separator means for recleaning the light impurity particlesdischarged from 'said fifth outlet, said light particle second-stageseparator means comprising a second housing containing a chamber andhaving at its upper end a fifth inlet for tangentially introducing intothe chamber the lighter particles to be cleaned, a ninth outlet at itslower end for returning to the first inlet the heavier particlesseparated in said second housing, and a tenth outlet for dischargingfrom the upper central portion of said second housing the final lightrejects.

9. The method of separating from a suspension cellulose pulp fibers, andparticles of impurities having a specific gravity lower than that of thepulp fibers, which comprises the steps of a. introducing the suspensiontangentially into an inlet opening arranged at the upper end of atotally cylindrical hydrocyclone chamber, said chamber having at itslower end a pulp fiber outlet opening and at its upper end a lightimpurity particle outlet opening, said suspension being introduced intosaid chamber at a pressure producing a pressure drop of about 5 psig.whereby the heavier pulp fiber particles are centrifugally displacedoutwardly and flow downwardly in a helical path toward the bottom of lthe hydrocyclone chamber and wherein the lighter particles are displacedradially inwardly and downwardly in the chamber;

b. diverting the light impurity particles upwardly in a vortex towardthe upper end of the hydrocyclone chamber by means of a conical divertersupported above the bottom wall of the chamber at an elevation above thepulp fiber outlet opening by means of a cylindrical support memberhaving an outer diameter which corresponds with the maximum diameter ofthe conical diverter;

c. removing the pulp fibers adjacent the bottom of the chamber; and

d. removing the light impurity particles from the top of the chamber.

1. the upper side wall portion of said lower chamber containing a firstinlet connected with said suspension supply means for supplying saidsuspension tangentially into said lower chamber;
 1. the upper portion ofsaid housing side wall containing an inlet opening connected with saidsuspension supply means for supplying said suspension tangentially intothe upper end of said chamber;
 1. The method of separating from areclaimed wastepaper suspension the cellulose pulp fibers and heavy andlight particles of impurities having specific gravities greater andless, respectively, than that of the pulp fibers, which comprises thesteps of a. supplying the suspension tangentially at a pressure of about30-50 psig. into the upper end of a high-pressure centrifugalhydrocyclone separator chamber; b. withdrawing the heavy impurityparticle rejects from the bottom of the high-pressure chamber, whereby avertical vortex of light impurity particles and pulp fibers is formed inthe center of the high-pressure chamber; c. withdrawing from the upperend of the high-pressure chamber the second suspension including thepulp fibers and the light impurity particles; d. supplying the secondsuspension at a pressure of about 5 psig. tangentially into the upperend of a low-pressure hydrocyclone chamber; e. withdrawing from thebottom of the low-pressure chamber a third suspension including the pulpfibers that flow helically downwardly adjacent the wall of thelow-pressure chamber, whereby the light particles are displaced radiallyinwardly and downwardly in the low-pressure chamber; f. diverting thelight particles upwardly to form a vortex flow thereof in the centralportion of the low-pressure chamber; and g. withdrawing from the top ofthe low-pressure chamber a fourth suspension including the lightimpurity particles.
 2. The method as defined in claim 1, and furtherincluding the steps of h. supplying the fourth suspension tangentiallyat a pressure of about 5 psig. to the upper end of a second low-pressurechamber; i. withdrawing from the bottom of the second low-pressurechamber the suspension including reclaimable pulp fibers and returningthis suspension to the original suspension; and j. withdrawing from theupper end of the second low-pressure chamber the final light impurityparticles.
 2. the lower end of said housing containing a first outletopening;
 2. the lower end of said lower chamber containing a firstoutlet;
 3. the central portion of the upper end of said lower chambercontaining a second outlet;
 3. the central portion of the upper end ofsaid housing containing a second outlet opening; c. upwardly convergentconical diverter means centrally mounted on the bottom wall of saidvertical hydrocyclone chamber, said diverter means including an upwardlyconvergent conical diverter member, and cylindrical support meanssupporting said conical diverter member a given distance above saidhousing bottom wall and above said first outlet opening, saidcylindrical support means having an outer diameter which correponds withthe maximum diameter of said conical diverter member; and d. tubularbaffle means connected with the central portion of the housing top walland communicating at its upper end with the second outlet opening, thelower end of said baffle means extending downwardly in said chamber to alevel slightly below that of said inlet opening; e. the pressure of saidsuspension supply means being such as to establish a pressure differenceof about 5 psig. between said inlet opening and said first outletopening, whereby the pulp fibers are separated from the suspension bycentrifugal force and pass downwardly in the chamber in an outer helicalpath adjacent the side wall surface of the chamber for discharge viasaid first outlet, said diverter means establishing in the centralportion of the chamber within the outer helical path an upwardlydirected small helical vortex flow of the impurity particles of thesuspension for discharge via said second outlet opening.
 3. The methodas recited in claim 2, and further including the steps of k. feeding asuspension including the heavy impurity particles discharged from thehigh-pressure centrifugal hydrocyclone chamber to the upper end of asecond high-pressure centrifugal hydrocyclone chamber; l. withdrawingfinal heavy impurity particles from the lower end of the secondhydrocyclone chamber; and m. returnIng to the suspension source of atleast one of the high-pressure hydrocyclone chambers from the upper endof the second high-pressure hydrocyclone chamber the suspension whichincludes reclaimable cellulose pulp fibers.
 4. Low-pressure dropapparatus for separating from a liquid suspension cellulose pulp fibersand particles of impurities having a specific gravity less than that ofthe cellulose pulp fibers, comprising a. means for supplying saidsuspension under pressure; b. a housing having top, bottom and sidewalls defining a vertical hydrocyclone chamber, said housing beingcylindrical and having a uniform diameter throughout its length,
 4. thecentral lower portion of said intermediate chamber containing a secondinlet communicating with said second outlet;
 5. the side wall portion ofsaid intermediate chamber containing a third outlet;
 5. Combinedhigh-pressure-drop low-presure-drop apparatus for separating from aliquid suspension cellulose pulp fibers, and first and second groups ofimpurities having specific gravities greater than and less than that ofsaid pulp fibers, respectively, comprising a. means for supplying saidsuspension under pressure; b. a unitary housing including a lowerportion containing a vertically arranged downwardly convergent conicalhigh-pressure-drop hydrocyclone separation chamber, an upper portioncontaining a vertically arranged generally cylindrical low-pressure-dropseparation chamber, and a middle portion containing an intermediatechamber,
 6. Apparatus as defined in claim 5, wherein said fourth outletis connected with atmosphere and said suspension supply means has apressure of about 30 to 50 psig, said lower chamber having a dischargepressure at said second outlet of about 5 psig.
 6. the upper side wallportion of said upper chamber containing a third inlet connected withsaid third outlet for introducing the suspension tangentially into theupper end of said upper chamber;
 7. the lower side wall portion of saidupper chamber containing a fourth outlet; and
 7. Apparatus as defined inclaim 5, and further including second-stage heavy particle hydrocycloneseparator means for recleaning the heavy impurity particles dischargedfrom first outlet, said second-stage separator means being of thetwo-body type including a conical housing which is divided into upperand lower chambers by a horizontal baffle, said separator meansincluding a fourth inlet for introducing the heavy particles from saidfirst outlet tangentially into the upper end of the upper chamber ofsaid second-stage separator, a sixth outlet (162) for discharging thefinal heavy rejects from the lower end of the lower chamber of saidsecond-stage separator, a seventh outlet (166) for returning to theheavy particle rejects discharged from the first outlet the lighterimpurity particles that are displaced upwardly in the central portion ofsaid lower chamber, and an eighth outlet (164) for returning to thefirst inlet the lighter particles that are directed upwardly in thecentral portion of said upper chamber.
 8. Apparatus as defined in claim5, and further including light particle second-stage separator means forrecleaning the light impurity particles discharged from said fifthoutlet, said light particle second-stage separator means comprising asecond housing containing a chamber and having at its upper end a fifthinlet for tangentially introducing into the chamber the lighterparticles to be cleaned, a ninth outlet at its lower end for returningto the first inlet the heavier particles separated in said secondhousing, and a tenth outlet for discharging from the upper centralportion of said second housing the final light rejects.
 8. the top wallportion of said upper chamber coNtaining a fifth outlet; and c. upwardlyconvergent conical diverter means centrally mounted on the bottom wallof said chamber, said diverter means including an upwardly convergentconical diverter member, and means supporting said diverter member agiven distance above said housing bottom wall, whereby in said lowerchamber the first group of impurities is separated from said suspensionby centrifugal force for discharge via said first outlet, the remainingpulp fiber particles and second group of impurities having an upwardlydirected vortex flow within said lower chamber for tangentialintroduction into said upper chamber via said second outlet, said secondinlet, said intermediate chamber, said third outlet and said thirdinlet, whereby the pulp fibers are separated by centrifugal force fromsaid suspension in said upper chamber for discharge via said fourthoutlet, and said diverter means cause said second group of particles toform an upwardly directed vortex in the central portion of said upperchamber for discharge via said fifth outlet.
 9. THE METHOD OF SEPARATINGFROM A SUSPENSION CELLULOSE PULP FIBERS, AND PARTICLES OF IMPURITIESHAVING A SPECIFIC GRAVITY LOWER THAN THAT OF THE PULP FIBERS, WHICHCOMPRISES THE STEPS OF A. INTRODUCING THE SUSPENSION TANGENTIALLY INTOAN INLET OPENING ARRANGED AT THE UPPER END OF A TOTALLY CYLINDRICALHYDROCYCLONE CHAMBER, SAID CHAMBER HAVING AT ITS LOWER END A PULP FIBEROUTLET OPENING AND AT ITS UPPER END A LIGHT IMPURITY PARTICLE OUTLETOPENING, SAID SUSPENSION BEING INTRODUCED INTO SAID CHAMBER AT APRESSURE PRODUCING A PRESSURE DROP OF ABOUT 5 PSIG. WHEREBY THE HEAVIERPULP FIBER PARTICLES ARE CENTRIFUGALLY DISPLACE OUTWARDLY AND FLOWDOWNWARDLY IN A HELICAL PATH TOWARD THE BOTTOM OF THE HYDROCYCLONECHAMBER AND WHEREIN THE LIGHTER PARTICLES ARE DISPLACED RADICALLYINWARDLY AND DOWNWARDLY IN THE CHAMBER; B. DIVERTING THE LIGHT IMPURITYPARTICLES UPWARDLY IN A VOTEX TOWARD THE UPPER END OF THE HYDROCYCLONECHAMBER BY MEANS OF A CONICAL DIVERTER SUPPORTED ABOVE THE BOTTOM WALLOF THE CHAMBER AT AN ELEVATION ABOVE THE PULP FIBER OUTLET OPENING BYMEANS OF A CYLINDRICAL SUPPORT MEMBER HAVING AN OUTER DIAMETER WHICHCORRESPONDS WITH THE MAXIUM DIAMETER OF THE CONICAL DIVERTER; C.REMOVING THE PULP FIBER ADJACENT THE BOTTOM OF THE CHAMBER; AND D.REMOVING THE LIGHT IMPURITY PARTICLES FROM THE TOP OF THE CHAMBER.